Insulated electrical conductor



A. RHEINER 2,017,607

INSULATED ELECTRI CAL CONDUCTOR Oct; 15, 1935.

Filed June 50, 1951 /70/10- 15b D/aCe'yc Cellulosj/c fibres,

nventor Patented` Oct. l5, 19,35

INSULATED ELECTRICAL CONDUCTOR Alfred Rheiner, Basel, Switzerland, assigner to the firm of Chemical Works Formerly Sandoz,

Basel, Switzerland Application June 30, 1931, Serial No. 547,893 i In Germany July 8, 1930 3 Claims. (Cl. 173-264) This invention relates to insulated electrical conductors, such as bars, plates, strips, wires andl the like.

It is known that cotton yarn can be used for the insulation of electrical conductors. Cotton, however, has various drawbacks in such use, as for example, a close dependence on the moisture of the atmosphere as well as on the pressure which is exerted on the insulating layer. This is evident particularly in the case of conductor wires which are wrapped together.

It has now been found that the monoto diacetylated cellulose fibres in which the original structure is maintained without alteration can ,advantageously be used as insulating material for electrical conductors of any kind.

The superiority of these iibres as electrically insulating material in comparison with unaltered cellulose ilbres is determined by their better speciilc insulating properties, their much less hygroscopicity and their great independence of the pressure to which the insulating material is subjected.

According to the present invention therefore it is proposed to use as an insulating material the monoto diacetylated cellulose bres in which the original structure is maintained without alteration, prepared ior example by the processes described in the British Patents Nos. 5,016/ 1907, 280,493, 314,913, 323,500, 324,630, 323,548, 323,515 and in the German Patents Nos. 224,330, 347,130, 380,994 or by any other process.

Further according to the present invention an electrical conductor can be prepared by covering a metal Wire, strip, plate or the 'like with layers or fibres of cellulose monoto diacetate, prepared according to any acetylation process which causes no structural alteration of the fibres.

The invention may be applied to any electrical apparatus, such as condensers and other appa- The following numerical data were found in the determination of the continuous current resistance of such an insulation, for example, with a yvoltage of 120 and an insulating layer oi 0.2 mm. thickness which was rolled on a cylinder l and which had a totalsurface area of 0.6314

sq. dm. y

Ohmic resistance (1) Bleached cotton yarn 50/1 505.510f5 il (2) Mo n o acetylated 'cellulose obtained according to the British m Patent No. 280,493 9821.7 l0 n These figures show the great superiority ,of the new insulating material inlcomparison with cotton. l5

In the investigations of the independence of the resistance of such insulating layer to the outer pressure exerted thereunto, the following figures were obtained: f a

n Ohmie resistanlce of Pressure per Olg blelig lclelllililosttiailxg www' mmm/1 resinas.:

0.1850 kg. 2111.10 1 a 4050.10 n 0.5555 kg. 112.10 n 4037-10 o 0.9250 kg. 13s-10 n 3015.10 n 1.2053 kg 118.10m 3915.10.91:

The results obtained show that with an n- 30 crease of' 1.11 kg./cm2 the ohmic resistance of the cotton decreased by 45.87%, whereas monoacetylated cellulose showed a decrease of only 3.58%. 35

The following table shows results obtained by the National Physical Laboratory in Teddington, Middlesex', England, in testing samples of acetylated fibres manufacturediaccording to the proc- 0 ratus where electrical insulation is required. ess of the British Patent No. 280,493. o Resistance between copper and brass cylinder (100 turns) (2) Normal atmosphere s win insulated with one severing o1: (1) Dry l (3) Sluh? (by 5 (a) 47% rel. moisture (b) 50% ml. moisture Megohms Meaohml Megohm: 1. ,Acetylated libre according to the Brit- 0.25 million. 00 thousand 33 thousand 0.4 megohms,

ish Patent No. 280,493, Sample A. 2. Acetyinted libre according to the Brit- 0.18 million 41 thousand 26 thousand 0.4 megohms. 5

ish Patent No. 280,493, Sample B. h 3. Aoetylated fibre according to the Brit- 0.40 million. 25 thousand 0.3 megohms.

ish Patent No. 280,403. Sample C. 4. 66's cellulose triacetate silk 7 thousand 2.2 megohms. 5. Natural silk 6 hundred.--. 2 thousand ohms. 6. Tomah l hun 2 thousand ohms. 7 80's cotton--.. l R 2 thousand ohms. u

The present invention is therefore of great technical value and shows a great advance in the insulation of electrical conductors, as it permits of the use oi a new nbrous material which, on account oi' its cheapness and its properties, canbeusedalasubstituteiorsilk.

The monoto diacetate cellulose libres may be used for the purpose claimed alone or in conjunction with other insulating materials. 'Ihey can for instance be wound directly on a metallic wire and then be covered with a suitable lacquer or they can be wound on the wire previously covered with a known insulating layer.

A number oi' illustrative embodiments oi the present invention are shown, by way of example, on the accompanying sheet of drawing. whereon Hg. 1 is a section along line I-I oi Fig. la.

ll'ig.iaisa'.sideelevationofaportionota metallic conductor provided with an insulation according to the present invention, parts being broken away and unraveled for the sake of clearness:

Fig. 2 is a sectional view along line 1 2 of Fig. 2a:

Fig. 2a is a view similar torig. la, but showing a second embodiment o! the invention;

Fig. 3 is a section taken on line 3-3 of Fig. 3a:

Fig. 3a is a view similar to Fig. la, showing still another embodiment of the invention.

Referring to the form shown in Figs. l and la, reference character' a designates a conventional metallic conductor oi' electricity surrounded with an insulating layer or layers b which consists of helically wound threads ot monoto diacetylated cellulose made in accordance with the present invention. 'Ihe suprpsed layers may be wound in different directions. as shown.

In the form shown in Figs. 2 and 2a, a conventional insulating layer c has been substituted i'or one of the layers b oi the embodiment aioredes scribed. Layer c may preferably contain some oi the lower acetylated cellulose acetate, according to the invention as hereinbeiore set iorth.

In the embodiment of Figs. 3 and 3a, the insulating lwer b, o! monoto diacetylated celiu- 1o lose ilbers, is encompassed by an outer layer o! lacquer.

It is evident that details of the constructions described may be changed without departing from the spirit ot the invention. l5

What I claim is:-

l. A metallic conductor for electrical purposes provided with an insulation containing a cellulose acetate of the group consisting oi' the monoand di-acetates prepared ytrom natural cellulose ma- 20 terial'without' alteration oi the original ilbrous structure ot the latter.

2. Ametallic conductor for electrical purposes provided with an insulation containing cellulose monoand di-acetates prepared from natural z5 cellulose material without alteration o! the orig inal ilbrous structure of the latter.

3. A metallic conductor tor electrical purposes provided with an insulation containing monoacetylated cellulose prepared from natural celso lulose material without alteration of the original ilbrous structure of the latter, the ohmio resistance ot the said insulation being relatively independent of external pressure which may be exerted thereon. g5

AIJ'REDRHEDTER. 

